Beak Color Research Articles

Developmental thermal conditioning regulates oxidative state and beak coloration in response to thermal stressors in adulthood

Developmental thermal conditioning regulates oxidative state and beak coloration in response to thermal stressors in adulthood

Characteristics of Several Qualitative Traits of Betet Chickens Raised by Fighting Cock Fans in Central Lombok

The study was conducted to determine the characteristics of betet chickens kept by fighting cock enthusiasts in Central Lombok. Determining the research area was carried out using the cluster sampling method, and sampling of farm was carried out non-randomly using the snowball method, and determining the number of chicken samples for observation was carried out using the accidental sampling method. Observations were made on 74 male Betet and 26 female Betet birds The variables observed were: body posture, feather color, beak color, beak shape, shank color and comb shape. The data obtained were tabulated, the frequency was calculated and analyzed using descriptive analysis. The results of the research found that the feather color of male betet chickens was dominated by bing (black), followed by green, brumbun and the smallest frequency of lurik colors. The feather color of female betet chickens was dominated by the alap color, followed by the kelawu color and the lowest frequency of the berumbun color. The highest frequency of beak color was yellow, followed by black, and the majority was sharply curved. The highest frequency of shank color in male betet chickens was yellow, followed by black and the lowest frequency was white. There were no white shanks found in female betet birds. The highest frequency of the comb shape for male betet chickens was without a comb because it is cut, followed by the single shape, then the lowest frequency was the pea shape. The majority of female betet chickens have a single comb, the rest do not have a comb (the comb does not develop). It was concluded that betet chickens kept by fighting cock enthusiasts

Phenotypic Characterization and Husbandry Practice of Indigenous Chicken Ecotypes at West Guji, Ethiopia

This study was conducted with the objectives of characterization of indigenous chicken ecotypes and their husbandry practice at West Guji. A total of 204 households were randomly selected from two purposively selected woredas and 612 mature chickens were used for qualitative and quantitative traits data collection. The collected data were analyzed using the Statistical Package for Social Sciences (SPSS Version, 20) and the General Linear Model procedure (PROC GLM) of SAS. The qualitative data of feather distribution, plumage color, beak color, eye color, comb types, earlobe color, head shape, and shank color were collected. The result showed a significant difference between the districts (P< 0.05). Further, wing span, chest circumstance, body weight, and body length quantitative data were also recorded. The result revealed that there was a significant difference in quantitative traits in the study areas (P< 0.05). Egg production potentials, body weight, plumage color, hatchability, growth rate, and mothering ability were traits preferred by the household for female selection. The average age at first egg laying of indigenous chicken was 6.69±0.36 months and the number of eggs per hen per clutch was 12.16±0.26. The current finding revealed that about 93.5% of the observed chicken’s ecotypes were feathered and 6.45% were naked necks. The dominant chicken’s plumage colors identified were; brownish (29.28%), red (24.05%), and multicolor/ambesma (14.65%). The production systems practiced in the study area were extensive. Finally, phenotypic characterization of indigenous chicken ecotypes and performance evaluation should be supported by genetic characterization methods.

Study on changing disciplinarian of beak colors in ducks and the regulation network based on transcriptome sequencing

Beak color in ducks is a primary characteristic of local breeds and genetic resources. Among them, black beaks, a rare packaging trait of high-quality duck products, have attracted much attention. In this study, Runzhou White Created ducks (black beak) and white-feathered Putian black ducks (yellow beak) were used to construct the F2 generation resource population to study the changing discipline of beak color combined with the beak color statistics of gray-beaked ducklings of Runzhou White Created ducks. Subsequently, transcriptome sequencing was performed to identify genetic markers related to beak color. To explore the rules of beak color change and its regulatory network, trends, and trend analysis and weighted gene co-expression network analysis（WGCNA）were performed. The screening results were verified by real-time quantitative polymerase chain reaction. A large difference was observed between the beak colors of birds from the F1 generation at 0 and 42 d of age. The F2 generation results show that nearly half of the black-beaked ducklings become green-beaked; the proportion of black spots for gray- and patterned-beaked ducklings increases with age, with most becoming green-beaked. Moreover, the beak color darkened from the first day, and the gray color value decreased significantly from the second day. Transcriptome sequencing indicated that TYR was differentially expressed between black and yellow beaks at 4 to 6 wk of age, and trend and WGCNA analyses showed that EDNRB signaling pathway genes and MITF were highly expressed in the first week, and TYR, TYRP1, and DCT were highly expressed at 4 to 6 wk of age. Therefore, there is melanin synthesis and deposition after hatching for gray- and patterned-beaked ducklings, while the yellow pigment might be deposited in the epidermis of beaks for black-beaked ducklings. The EDNRB signaling pathway is probably involved in early melanosome maturation and melanin formation in duck beaks, and genes such as TYR can maintain the black-beak phenotype.

Identification of SNPs in MITF associated with beak color of duck.

Introduction: Beak color-a pigment-related trait-is an important feature of duck breeds. Recently, little research has addressed genetic mechanism of the beak colors in poultry, whereas the process and the regulation factors of melanin deposition have been well described. Methods: To investigate the genetic mechanism of beak colors, we conducted an integrated analysis of genomic selection signatures to identify a candidate site associated with beak color. For this, we used black-billed (Yiyang I meat duck synthetic line H1, H2, H3&HF) and yellow-billed ducks (Cherry Valley ducks and white feather Putian black duck). Quantitative real-time PCR and genotyping approaches were used to verify the function of the candidate site. Results: We identified 3,895 windows containing 509 genes. After GO and KEGG enrichment analysis, nine genes were selected. Ultimately, MITF was selected by comparing the genomic differentiation (FST). After loci information selection, 41 extreme significantly different loci were selected, which are all located in intron regions of MITF and are in almost complete linkage disequilibrium. Subsequently, the site ASM874695v1:10:g.17814522T > A in MITF was selected as the marker site. Furthermore, we found that MITF expression is significantly higher in black-beaked ducks than in yellow-beaked ducks of the F2 generation (p < 0.01). After genotyping, most yellow-billed individuals are found with homozygous variant; at the same time, there are no birds with homozygous variant in black-billed populations, while the birds with homozygous and heterozygous variant share the same proportion. Conclusion: MITF plays a very critical role in the melanogenesis and melanin deposition of duck beaks, which can effectively affect the beak color. The MITF site, ASM874695v1:10:g.17814522T > A could be selected as a marker site for the duck beak color phenotype.

Quantitative and Qualitative Characteristics (Phenotype) of Laying Ducks in Ternate City as the Basis for Local Livestock Breeding in North Maluku Province

Duck is a producer of animal protein whose production is eggs and meat, is a type of poultry that has the potential to be developed in the city of Ternate. However, until now there has been no characterization research in Ternate City. The aim of the study was to determine the phenotype characteristics as the basis for breeding local cattle in North Maluku. The materials used were adult male and female laying ducks, the variables observed were male ducks, qualitative characteristics were the character of coat color, beak color, eye color and quantitative characteristics were measured body size including femur length, tibia length, shank length, shank circumference, length wingspan, chest length, chest width, chest depth and hip width. calculating the mean formula, standard deviation and coefficient of diversity, qualitative characteristics of ducks using relative frequency analysis. The results showed that the quantitative characteristics of female ducks were more similar than those of male ducks. While the qualitative nature, the color is relatively the same both males and females have brown fur, only one is blackish brown, the skin color of the legs and beak is more dominantly black and brown compared to yellow, black yellow and brown yellow.

Pengaruh Pemberian Tepung Daun Indigofera Sebagai Pengganti Bungkil Kedelai Dan Dedak Dalam Ransum Terhadap Sifat Kualitatif Dan Kuantitatif Entog (Cairina moschata)

This study was conducted to analyze the effect and level of indigofera leaf flour as a substitute for soybean meal and rice bran in the ration on qualitative and quantitative properties. This research was conducted on March 30, 2021 to April 27, 2021. The study was conducted experimentally using a Completely Randomized Design (CRD). This study consisted of five types of treatment in the form of ration formulations, namely P0 = without the addition of indigofera leaf meal (TDI) as control feed, P1 = 25% addition of TDI, P2 = 50% addition of TDI, P3 = 75% addition of TDI and P4 = 100% the addition of TDI was given to 80 muscovy duck placed in cages that had been divided into 20 parts, each part was filled with 4 muscovy ducks. The variables observed in this study were qualitative traits including coat color, beak color, shank color, caruncle color and skin color and quantitative traits included body weight, body circumference, beak length, chest length, femur length, tibia length, tibia circumference, length shank and wing length. The data from the qualitative research were analyzed descriptively, while the quantitative traits were analyzed using the Analysis of Variance or Anova (Analysis of Variane) and further tested using the Duncan Multiple Range Test. The results showed that the provision of indigofera leaf flour in the ration at P4 showed a shiny and thicker coat color and had a significant effect on tibia circumference (P&lt;0.05)

PERFORMA KUALITATIF DAN KUANTITATIF AYAM KAMPUNG (Gallus Gallus Domesticus) DI PETERNAKAN PEMBIBITAN THE MOTHER

This study aims to identify the quantitative and qualitative performance of native chickens in The Mother breeding farm. This study used 50 male native chickens and 50 female native chickens aged 7 months. Variables observed included body hair pattern color, comb shape, comb color, shank color, eye color, beak color, body weight, chest circumference, shank length, shank circumference, body length, pubic bone length to chest, pubic bone distance and length wing span. Data were analyzed using descriptive analysis. The results of this study indicate that the body color of the male is Columbian (100%), while the female is solid black (62%), columbian (22%) and speckled or dotted (16%). The male cockscomb is pea (86%) and single (14%), while the female is pea (70%), walnut (20%) and single (10%). The color of the male comb is red (100%), while the female is red (98%) and black (2%). The shank color of males is yellow (74%), black (14%) and white (12%), females are black (74%), white (16%) and yellow (10%). Male eye color is orange (76%) and yellow (24%), while females are orange (66%), yellow (20%) and brown (14%). The color of the male's beak is yellow (54%), black and yellow (38%) and white (8%), while the female's beak is black and yellow (82%), yellow (10%) and white (8%). The results of the quantitative characteristics of the study showed that the male body weight was 2.22 ± 2.02 kg and the female was 1.71 ± 0.25 kg, the male chest circumference was 33.9 ± 3.68 cm and the female was 30.67 ± 2.08 cm, the length male shank 9.61 ± 0.89 cm and female 27 ± 0.59 cm, male shank circumference 5.52 ± 0.65 cm and female 4.4 ± 0.5 cm, male body length 20.27 ± 1.17 cm and female 20.40 ± 2.27 cm, the length of the pubic bone to the chest of the female is 7.87 ± 1.06 cm, the distance between the pubic bones is 2.8 ± 0.49 cm, the length of the male wing span is 23.28 ±2.18 cm and females 16.61±2.44 cm. The conclusion of this study is that the quantitative and qualitative characteristics of free-range chickens on The Mother farm are diverse and selection can be made. Keywords: Domestication chicken, Selection, Quality breeds, Lampung Province

Identifikasi Fenotip Generasi Induk (G0) dan Generasi Pertama (G1) Pola Perkawinan Assortative terhadap Hasil Produksi Pada Ayam Kokok Balenggek

AKB is a native chicken from West Sumatra. The Minang people reportedly call it Balenggek chicken which has a cascading rhythmic crowing sound. AKB comes from crosses of the Red Junglefowl (Gallus gallus) with local chickens. AKB is a source of wealth for local livestock in Indonesia that needs to be protected and preserved . This research consisted of two stages. The first stage of the research aimed to identify the qualitative and quantitative characteristics and the second stage of the research aimed to determine the first generation phenotype (G1) resulting from the Assortative mating pattern on production in IMR. This second stage of research used 8 male AKBs. and 48 females that are sexually mature. Based on the results of the identification of qualitative and quantitative characteristics research, it shows that the qualitative characteristics of male AKB based on feather pattern are dominated by columbian type, striated feather pattern, silver and gold flickering feathers, yellow/white shank color, single type comb shape, yellow/white beak color . Based on the pattern of feathers, the female AKB is dominated by the columbian type, striated feather pattern, golden feather flickering, yellow/white shank color, single comb type and yellow/white beak color. The coefficient of diversity of high quantitative traits in male AKB is neck diameter (22.22%), comb height (18.45%) and for females is comb height (29.60%) and body weight (18.77%) . Based on the results of the second phase of the study, the average weight of DOC IMR was 24.31 grams. Mating based on the similarity of fur color, produces offspring with the same fur color as their parents. P1, P2, P3, P4 relatively the same growth pattern.

Effect of Beak Color on Growth Performance and Carcass Characteristics of Pekin Ducks

Background: Pekin ducks are broadly raised over the world, particularly in Asia continent, moreover, they are famous for the delightful taste of Beijing roast duck around the world. The aim of this study was to explore the effect of beak color on growth performance, carcass traits and sexual dimorphism of Pekin ducks. Methods: A total of 250 one-day-old Pekin ducks were separated according to beak color into two groups, yellow beak (YB) and blue beak (BB). Body weight and body weight gain were recorded from the first week to the marketing age (6 wks). Carcass traits were taken at the marketing age (20 ducks /each phenotype). Sexual dimorphism was calculated for live body weight and carcass traits at marketing age. Result: show that YB ducks have significantly heavier body weight at 1 and 5 wks of age compared to BB, however the body weight of BB ducks was higher at 3 and 4 wks of age. At marketing age, the differences in body weight between two phenotypes were not significant. Generally, BB ducks have significantly higher body weight gain and growth rate compared to YB ducks. The mortality and defect ratio were affecting beak color, the blue beak ducks recorded higher relative mortality rate and lower defect ratio compared to yellow beak ducks. There was no effect of beak color on carcass traits. However, the sexual dimorphism was significantly higher for the YB ducks for most traits compared to BB. In conclusion, we concluded has a significant effect beak color on growth performance and sexual dimorphism of Pekin ducks.

Qualitative Traits of Muscovy duck (Cairina moschata) in Ciayumajakuning, West Java, Indonesia

Qualitative traits can be used as a reference for entog development and conservation. Qualitative traits are indispensable for selection based on phenotypics such as plumage color, beak color, and shank color. The research objective was studied the qualitative traits of entog in Ciayumajakuning (Cirebon, Indramayu, Majalengka, dan Kuningan). This research uses survey method with sampling technique of multistage probability random sampling. The research object observed are 673 Muscovy ducks consisting of 309 drake and 364 duck. Data analysis applies descriptive qualitative analysis method. The results of research show that duck Muscovy ducks plumage colors are dominated by black and white (44.78%), only white (28.30%), and only black (17.86%); while drake are dominated by only white (45%), black and white (35.9%), and gray (7, 77%). The duck beak colors are dominated by black (25.82%), black and white (20.60%), and pink (23.63%); while drake beak colors include pink (38.80%), black (21.00%), and black and white (19.40%). Duck shank colors are dominated by black (39.29%), white (27.29%), and yellow (18.68%); while drake shank colors, among others, are yellow (41.70%), black (29.80%), black and white (12.00%). Based on the results of the study, it can be concluded that the qualitative traits of Muscovy duck in Ciayumajakuning are quite diverse.

Status of Indigenous duck and duck production system of India - a review.

Duck genotypes in India are generally grown in extensive conditions by small breeders. The purpose of breeding is to obtain meat and eggs to contribute a small amount to the family budget. These duck genotypes are known for their adaptability to the environment and their resistance to diseases. As per livestock census 2019, the duck population of India is 33.51 million constituting 4.0% of the total poultry population. Ducks are most abundant in Eastern (64.5%), North Eastern (16.02%), and Southern (12.60%) states of India. In most of the places, poultry farmers prefer rearing indigenous ducks under scavenging system. The flock sizes of ducks ranged from 2 to 9 ducks among different households in the surveyed locations. Plumage color and beak color are not defined in indigenous ducks. There is inter-individual variation in morphological and yield traits. The average first laying age in indigenous ducks ranges from 145 to 223days and 17.0-38.5% owners do not supply any additional feed to their ducks. The mortality rate among chicks was observed to be higher at younger ages. The average annual egg productions per indigenous duck are very poor. However, most of the duck farmers earned a good amount of subsidiary income from duck rearing. Hence, selective breeding as a genetic tool could be utilized to improve the productivity of indigenous ducks.

Genome-Wide Analysis Identifies Candidate Genes Encoding Beak Color of Duck.

Beak color diversity is a broadly occurring phenomenon in birds. Here, we used ducks to identify candidate genes for yellow, black, and spotted beaks. For this, an F2 population consisting of 275 ducks was genotyped using whole genome resequencing containing 12.6 M single-nucleotide polymorphisms (SNPs) and three beak colors. Genome-wide association studies (GWAS) was used to identify the candidate and potential SNPs for three beak colors in ducks (yellow, spotted, and black). The results showed that 2753 significant SNPs were associated with black beaks, 7462 with yellow, and 17 potential SNPs with spotted beaks. Based on SNP annotation, MITF, EDNRB2, members of the POU family, and the SLC superfamily were the candidate genes regulating pigmentation. Meanwhile, isoforms MITF-M and EDNRB2 were significantly different between black and yellow beaks. MITF and EDNRB2 likely play a synergistic role in the regulation of melanin synthesis, and their mutations contribute to phenotypic differences in beak melanin deposition among individuals. This study provides new insights into genetic factors that may influence the diversity of beak color.

Experimentally reduced feather microbial loads improve reproductive performance in captive Zebra Finches

AbstractWe performed a laboratory experiment on caged, domesticated Australian Zebra Finches (Taeniopygia guttata castanotis) to assess the effects of antimicrobial treatment applied to birds’ plumage on the feather microbial loads of breeding pairs and their associated reproductive performance. Treatments included an experimental group that experienced frequent misting with a broad-spectrum antimicrobial, as well as 2 control groups. Microbial loads (colony forming units [CFUs]) sampled from the belly feathers of breeders were higher posthatching than prehatching, and experimental pairs had lower loads (one-half to one-third the CFU counts) than controls at all sampled breeding-cycle stages. Clutch size and hatching success did not differ among treatments, but experimental pairs fledged nearly 50% more offspring (mean = 3.5 per clutch) than controls (mean = 2.3 per clutch) due to experiencing much lower nestling mortality. Offspring development rate, as assessed by one metric, varied among treatments: beak color score sampled midway in the development of adult phenotype revealed that offspring of experimental pairs had more rapid development. Findings imply that experimentally reduced density of feather microbial loads on breeders decreased reproductive costs in the posthatch phase, resulting in increased offspring survival and condition. At the time offspring fledged, uropygial gland volume tended to be greater among breeders that had experienced antimicrobial application throughout the breeding cycle. These results are consistent with a growing literature showing that the feather microbiome contributes significantly to the evolution of avian life histories and behavior and indicate that Zebra Finches are a useful laboratory model for investigating in vivo effects of the feather microbiome on avian hosts.

Phenotype Characteristics of Alabio Ducks (Anas Platyrhynchos Borneo) in South Kalimantan

Research on the phenotype characteristics of Alabio Ducks (&lt;em&gt;Anas Platyrhynchos&lt;/em&gt; Borneo) in South Kalimantan was conducted to determine the phenotypic characteristics of 3 central Alabio ducks (Hulu Sungai Utara, Banjar and Tabalong Regencies). The materials used in this study were 480 Alabio ducks, aged ± 6 months, consisting of 30 males and 450 females. The method used in this research was a survey method that was multistage random sampling. The variables observed were dominancy and pattern colors of feathers on neck, breast, back, wing, leg, and tail, beak color and shank color. Based on the results of observations in the Tabalong, HSU and Banjar Regencies, the results show that Alabio ducks have 6 kinds of colors that appear on observed body parts, namely black, grayish-white, blackish-gray, brownish-gray, brown, brownish-white, black, and brownish-white, light-brown spots or dark brown spots on breast feather. The colors of the beak and shank of male and female Alabio ducks are light-yellow or whitish yellow. While the uniform color characteristics are found in male and female Alabio ducks, namely on the grayish-white neck feathers, blackish gray and bluish green on wing feathers, blackish and brownish gray on back-feathers, brownish and black gray on tail-feathers and brownish-white, light brown spots. or dark brown spots on breast-feather. In conclusion, there are not many differences in both the dominant feather color, the variation in the color of the feathers, the beak, the shank of the Alabio ducks, since most of them come from the similar ancestors.

A multispecies BCO2 beak color polymorphism in the Darwin’s finch radiation

Carotenoid-based polymorphisms are widespread in populations of birds, fish, and reptiles,1 but generally little is known about the factors affecting their maintenance in populations.2 We report a combined field and molecular-genetic investigation of a nestling beak color polymorphism in Darwin's finches. Beaks are pink or yellow, and yellow is recessive.3 Here we show that the polymorphism arose in the Galápagos half a million years ago through a mutation associated with regulatory change in the BCO2 gene and is shared by 14 descendant species. The polymorphism is probably a balanced polymorphism, maintained by ecological selection associated with survival and diet. In cactus finches, the frequency of the yellow genotype is correlated with cactus fruit abundance and greater hatching success and may be altered by introgressive hybridization. Polymorphisms that are hidden as adults, as here, may be far more common than is currently recognized, and contribute to diversification in ways that are yet to be discovered.

PSVI-14 Characteristic of hybrid chicken derived from crossing of Ogye and white leghorn

Abstract Ogye, an indigenous Korean chicken breed has entirely black external features and internal organs. White Leghron, an transboundary breed has white color features as opposed to Ogye. We make crossbreed (Ogye x White Leghorn) to investigate how the phenotype appeared in F1. In F0, 5 females and 1 male were selected for each parental type; 1) Ogye(♂) x White leghorn(♀), 2) White leghron(♂) x Ogye(♀). We A total of 321 individuals of F1 were made through artificial insemination. We measured body weights at birth, 8 weeks, 16 weeks, 24 weeks, and 32 weeks of age. In 1) type females, the average of body weight at each period was 39.04±0.32, 613.18±6.86, 1149.37±7.76, 1463.97±13.25, 1718.02±14.83 respectively. In 2 type females, that was 30.57±0.21, 543.19±7.54, 1069.63±12.92, 1410.06±10.80, 1527.53±13.73. The P-value values for each period were less than 0.05. In 1) type males, the average of body weight at each period was 39.18±0.34, 744.70±7.84, 1579.39±15.76, 2014.63±19.15, 2310.89±20.58. In 2 type females, that was 30.71±0.24, 683.75±9.51, 1419.79±15.76, 1800.00±18.88, 2064.79±19.68. The P-value values for each period were also less than 0.05. In the case of feather color, it was generally white, but black spots appeared only in females produced in type 1). Comb and beak color was generally also red, but black appeared only in in females produced in type 1). From these results, it can be estimated that paternal factors such as weight and appearance are greatly affected, and we plan to investigate the genetic patterns of each trait through F2 construction in the future.

Estimation of Genetic Parameters for Body Weight and Some Colour Traits in the Seventh-generation Index Selected Nigeria Heavy Local Chicken Ecotype

Background: This study was conducted to estimate the genetic parameters of body weight and some colour traits in seventh generation (G7) index selected Nigerian Heavy Local Chicken Ecotype (NHLCE) progenies at point of lay to 12 weeks. Methods: 5 sires and 12 hens were used to generate the progenies used for the experiment. Traits measured included weekly body weight, egg colour, beak colour and feather colour. Data collected were subjected to one way analysis of variance in a Paternal half sib analysis using Animal model of SAS (2003). Four weeks body weight measurements, egg colour, beak colour and feather colour for 5 sires ranged from 1.29±0.05 1.54±0.07; 2.55±0.02 to 4.00±0.02; 2.45±0.02 to 4.83±0.02 and 1.73±0.02 to 4.58±0.04 respectively. Result: The new Duncan’s multiple range test shows that sire families are similar (p greater than 0.05) in the body weight and beak colour, but significantly differed (p greater than 0.05) in the egg colour and feather colour. The heritability estimates of mature body weight for week 3 was medium, while estimates of heritability for weekly mature body weight for weeks 1, 2 and 4, egg colour, beak colour and feather colour of NHLCE were low heritability. Low h2 of traits suggest that progeny and pedigree selection could be employed for improvement of the egg colour, beak colour and feather colour of NHLCE. The study showed positive genetic correlations between beak colour and egg colour, negative genetic correlations between beak and feather colour. This means that no decision can be taken in isolation as the selection of one trait will have consequences on other traits.

Variation in carotenoid-containing retinal oil droplets correlates with variation in perception of carotenoid coloration

In the context of mate choice, males may vary continuously in their expression of assessment signals, typically reflecting information about variation in mate quality. Similarly, females may exhibit variation in mate preference, which could be due to differences in how individual females perceive signals. The extent to which perception varies across individuals, however, and whether differences in sensory physiology underlie perceptual differences is poorly understood. Carotenoid pigments create the orange-red coloration of many assessment signals, and they also play a role in color discrimination in many vertebrates via their presence in retinal oil droplets. Here, we link variation in oil droplet carotenoid concentration with the ability of female zebra finches (Taeniopygia guttata) to discriminate an orange-red color continuum that parallels variation in male beak color, a mate assessment signal. We have shown previously that zebra finch females perceive this color range categorically, meaning they label color stimuli from this continuum as belonging to two categories and exhibit better discrimination between colors from different categories as compared with equally different colors from within a category. We quantified behavioral color discrimination and R-type (red) cone oil droplet spectral absorption, a proxy for carotenoid concentration. Oil droplet absorption was strongly predictive of variation in behavioral color discrimination ability. In particular, higher carotenoid concentration in oil droplets correlated with increased discrimination of colors from different sides of the previously identified category boundary. These data show that differences in the sensory periphery can correlate with individual variation in perception of a signal-relevant color range.Significance statementSignal receivers vary in their preferences for signaling traits, but whether this is due to variation in how different receivers perceive signals is not well-understood. We show that variation between individual zebra finch females in perception of an orange-red continuum range correlates with the carotenoid concentration of retinal oil droplets. These data provide the first direct evidence that individual variation in oil droplet carotenoid concentration can lead to variation in color discrimination ability. Linking variation in signal-relevant color discrimination ability with variation in retinal physiology suggests a potential mechanism contributing to individual variation in signal assessment.

Beak coloration of starling (Sturnus unicolor) males depends on the length of their throat feathers

Abstract Within the context of complex sexual signaling, most research has focused on exploring the associations between several signals and/or their relationships with different proxies of individual quality. However, very few studies have focused on checking whether the expression of one signal is conditioned by the expression of the others. Here, by experimentally shortening the throat feathers of male spotless starlings (Sturnus unicolor), we evaluated the influence of this trait on the color expression of the beak base. In addition, we tested the relationship between these two sexually dimorphic characters with traits indicating individual qualities, such as body condition and color reflectance at the wavelength related to carotenes in the tip of the beak. Our results show that the coloration of the beak base in males, but not in females, is positively related to body condition and to the length of ornamental throat feathers. Moreover, the experimental shortening of throat feathers in males had a negative effect on the blue chroma intensity of their beak base 1 year after manipulation. These results support for the first time a causal link between the expression of two sexually dimorphic characters, which is essential to understand their functionality in a multiple signaling framework.